diff --git a/graphify/llm.py b/graphify/llm.py
index 46a4785d32..ff959e1918 100644
--- a/graphify/llm.py
+++ b/graphify/llm.py
@@ -1065,6 +1065,26 @@ def _parse_llm_json(raw: str) -> dict:
     return {"nodes": [], "edges": [], "hyperedges": []}
 
 
+def _anthropic_response_text(content, default: str | None = None) -> str | None:
+    """Return the first Anthropic content block that carries text.
+
+    Current Claude models emit a ``ThinkingBlock`` ahead of the ``TextBlock``
+    when extended thinking is enabled (including the default-on path where the
+    thinking text is omitted). Indexing ``content[0]`` therefore raises or
+    yields no text (#2697). Select on the block's type instead of its position.
+    """
+    if not content:
+        return default
+    for block in content:
+        block_type = getattr(block, "type", None)
+        if block_type is not None and block_type != "text":
+            continue
+        text = getattr(block, "text", None)
+        if isinstance(text, str) and text.strip():
+            return text
+    return default
+
+
 def _bedrock_response_text(resp: dict, default: str = "") -> str:
     """Return the first Converse content block that carries text.
 
@@ -1331,7 +1351,7 @@ def _call_claude(api_key: str, model: str, user_message: str, max_tokens: int =
         system=_extraction_system(deep=deep_mode),
         messages=[{"role": "user", "content": _anthropic_content(user_message, images or [])}],
     )
-    raw_content = resp.content[0].text if resp.content else None
+    raw_content = _anthropic_response_text(resp.content)
     result = _parse_llm_json(raw_content or "{}")
     result["input_tokens"] = resp.usage.input_tokens if resp.usage else 0
     result["output_tokens"] = resp.usage.output_tokens if resp.usage else 0
@@ -2602,7 +2622,7 @@ def _rec(inp, out) -> None:
         u = getattr(resp, "usage", None)
         if u is not None:
             _rec(getattr(u, "input_tokens", 0), getattr(u, "output_tokens", 0))
-        return resp.content[0].text if resp.content else ""
+        return _anthropic_response_text(resp.content, default="")
 
     if backend == "claude-cli":
         import platform, shutil, subprocess
diff --git a/tests/test_image_vision.py b/tests/test_image_vision.py
index 1071450273..fa9b6398fd 100644
--- a/tests/test_image_vision.py
+++ b/tests/test_image_vision.py
@@ -401,6 +401,53 @@ def test_bedrock_response_text_tolerates_malformed_blocks():
     assert llm._bedrock_response_text(resp, default="{}") == _NODE_JSON
 
 
+def test_anthropic_response_text_single_text_block_unchanged():
+    content = [SimpleNamespace(type="text", text=_NODE_JSON)]
+    assert llm._anthropic_response_text(content) == _NODE_JSON
+
+
+def test_anthropic_response_text_skips_leading_thinking_block():
+    content = [
+        SimpleNamespace(type="thinking", thinking="planning"),
+        SimpleNamespace(type="text", text=_NODE_JSON),
+    ]
+    assert llm._anthropic_response_text(content, default="{}") == _NODE_JSON
+
+
+def test_anthropic_response_text_legacy_block_without_type():
+    content = [SimpleNamespace(text=_NODE_JSON)]
+    assert llm._anthropic_response_text(content) == _NODE_JSON
+
+
+def test_anthropic_response_text_falls_back_without_text():
+    content = [SimpleNamespace(type="thinking", thinking="")]
+    assert llm._anthropic_response_text(content, default="SENTINEL") == "SENTINEL"
+
+
+def test_call_claude_parses_thinking_model_response(tmp_path, monkeypatch):
+    """Extended-thinking models must not crash on content[0] being ThinkingBlock."""
+    img, _, _ = _make_corpus(tmp_path)
+    refs = llm._build_image_refs([img], tmp_path)
+
+    class _Messages:
+        def create(self, **_kw):
+            return SimpleNamespace(
+                content=[
+                    SimpleNamespace(type="thinking", thinking=""),
+                    SimpleNamespace(type="text", text=_NODE_JSON),
+                ],
+                usage=SimpleNamespace(input_tokens=5, output_tokens=7),
+                stop_reason="end_turn",
+            )
+
+    mod = types.ModuleType("anthropic")
+    mod.Anthropic = lambda **_kw: SimpleNamespace(messages=_Messages())
+    monkeypatch.setitem(sys.modules, "anthropic", mod)
+
+    result = llm._call_claude("k", "claude-opus-4-6", "CORPUS", images=refs)
+    assert result["nodes"]
+
+
 def test_call_bedrock_parses_reasoning_model_response(monkeypatch):
     """End-to-end: a reasoning-model response must not look hollow."""
     def _fake(monkeypatch):